Here is mt suggestion for arena, we should be able to pick who we fight, if we are fighting a bronze level hero we get the bronze award for the wall so if we want to fight harder level like gold or silver when we beat that gold or silver hero we get the points gold or silver points for the wall. So if we can pick who we fight at what level we want  we claim the bronze silver gold points of the hero level we win. So we keep what we can kill..